This invention relates to a blade for a centrifugal pump impeller for high speed centrifugal pumps and to an impeller incorporating such blades.
The blade of the invention is particularly suitable for use in centrifugal pumps which operate approximately in the range of 3,000 to 30,000 RPM.
In the design of high speed centrifugal pumps for various purposes, it has been common to provide the impeller rotor with a plurality of blades which are effectively radial with respect to the axis of rotation. The blades themselves are generally of such a nature as to have front and rear faces which are parallel thereby providing a flat blade which has one flat surface facing in the pumping direction and one flat surface facing away from the pumping direction.
This type of centrifugal pump has suffered from a number of disadvantages, in particular, the low efficiency of the pump, of the order of 55-58%, the reduction in the pressure head provided by the pump at low flow rates, and the fact that a high NPSH value is required because of the shock losses in the suction even at the specified flow.
Furthermore, the disadvantage also exists with radial blades that the blade is required to support the full reaction force of the pumped fluid by virtue of its inherent structural strength and no balancing of this force is otherwise achieved.